Local exchange carrier access network equipment, such as Digital Loop Carriers (DLCs) and Digital Subscriber Access Multiplexers (DSLAMs), provide Digital Subscriber Line (DSL) service to subscribers over twisted wire pairs or “loops”. The electronic components and systems comprised by DLC's and DSLAM's are protected through the use of protection devices (surge protectors) located near the network equipment from damage by induced voltage surges (e.g., via lightning strikes) picked up by the twisted wire pairs. Such surge protectors are essentially transparent to the network services (Plain Old Telephone Service (POTS), Asymmetrical Digital Subscriber Line (ADSL), etc.) while they shunt momentary high voltage surges to ground. The protectors are also essentially transparent to metallic loop test systems that test for faults on the twisted wire pair between subscriber premise equipment and upstream network equipment.
When remote electronics, typically located on the outside of a subscriber's premise, are powered over the twisted wire pair from a network equipment site or another remote location, power feed equipment for providing power to such remote electronics is coupled to the twisted wire pair. When the network electronics are AC coupled to the twisted wire pair, the power feed equipment can be directly bridged to the twisted wire pair. However, when the network electronics are DC coupled to the twisted wire pair, as would typically be the case for a combination POTS/ADSL line card, simple direct bridging cannot be implemented. For example, the voltage provided by the power feed equipment (e.g., nominally −200 Vdc) conflicts with the POTS “talk battery” voltage (nominally −48 Vdc).
Conventional approaches to providing a DC voltage on a twisted wire pair from power feed equipment are known. In cases where POTS is not required, conventional combination POTS/ADSL cards are replaced by ADSL-only cards, thus allowing the power feed to be applied without any conflicts. In cases where POTS and ADSL functionality is facilitated, even though the POTS signal is unused, combination POTS/ADSL signals are passed through a high pass filter for eliminating unused POTS talk battery voltage, thereby allowing resulting filtered signals to be bridged with the power feed.
However, such conventional approaches for providing the DC power feed over the twisted wire pair have significant limitations associated therewith. In the case where conventional combination POTS/ADSL cards are replaced by ADSL-only cards, such a conventional approach would have an adverse expense associated with replacing POTS/ADSL combination cards that are already deployed in a network with newly developed ADSL-only cards. Furthermore, replacing conventional combination POTS/ADSL cards with ADSL-only cards would require rewiring in the DLC or DSLAM cabinets or require installation of cross-connect cabinets for connecting reassigned lines out of the DLC or DSLAM cabinets. In the case where a combined POTS/ADSL signal is filtered, such high pass filtering of a signal from a DLC or DSLAM will prevent complete metallic loop testing (MLT), as MLT uses the spectrum down to DC for many tests (e.g., detecting resistive faults, detecting presence of foreign voltages, etc). Additionally, it is hard to selectively gain access to an individual twisted wire pair because multi-pair cable harnesses and multi-pair connectors are often pre-wired with the equipment in cabinets, leaving little available space to accommodate access to additional pairs and for the high pass filtering equipment.
Accordingly, a solution for enabling the combination of surge protection, DSL signal transmission, full metallic loop testing and bridging of a DC power feed to be facilitated in association with a twisted wire pair in a manner that overcomes limitations associated with conventional solutions would be useful.